I promise you if you dont cut back on protein while you are raising ducklings or geese up you increase your odds for angelwing. This is 100% fact. If you dont believe me ask any other waterfowl breed
There are breeders who disagree. There is even a breeder with his own line of waterfowl feed and the breeder rations are 24% protein.
In the wild, ducks DO NOT get angel wing. Angel wing shows up in domestic ducks that get feed consisting of corn, soy and wheat and at parks where people feed ducks BREAD AND CRACKERS. A wild ducks diet is naturally high in protein, especially during the hatching season. They do stop in fields during fall migration and help themselves to a free corn dinner, but there isn't corn and soy available on a regular basis.
Wildlife officials have even been changing their tune about the cause of angel wing over the past few years...
"When wild ducks are fed human food (especially bread or crackers) their organs become engorged and fatty, which can cause them to suffer from heart disease, liver problems and other health complications. Bread also has very few nutrients, and can get compacted in a bird's crop. Many rehabilitators see "bread-impacted crop" in sick and distressed park ducks.
Waterfowl at artificial feeding sites are often found to suffer from poor nutrition. In a natural setting they will seek out a variety of nutritious foods such as aquatic plants, natural grains, and invertebrates. Bread is very low in protein, contains additives that wildfowl aren't built to cope with, and it's a very poor substitute for natural foods. Ducklings fed bread miss out in vital nutrients during their critical first few weeks, causing splay leg, angel wing, slipped tendons and other growing defects."
http://duckrescuenetwork.org/duck_care.html
"When a young bird eats calorie-dense, nutritionally poor foods like bread the growth of its feathers outpaces the development of its wing bones. Gravity pulls the heavy feathers down, and the growing bones twist outward, resulting in a syndrome known as Angel Wing. Bandages and physical therapy can correct the condition in young birds, but it is incurable in adults, and affected birds lose the ability to fly.
Parks and Recreation Horticulture Supervisor, Steve Nittolo, has spent several months working on ways to improve water quality in city park ponds. It all goes back to the public dumping bread into park ponds believing they are helping feed the wild ducks, when instead they are really harming them, Nittolo said."
http://www.spokanecity.org/services/articles/?ArticleID=1850
More...
http://seattletimes.nwsource.com/html/localnews/2008518282_birdjunkfood15m.html
Cutting protein in ducks only helps save money. It really isn't a big help for the bird. The fact that they can live with it doesn't mean it is optimal. After a few generations is when poor quality low protein feed becomes more of a problem. Fertility, health, etc... are all effected. If you are just raising birds to market weight, you wont notice the bad effects on your animals and it might be worth the risk for you.
I have spent the last 3 years studying endocrinology. Not because I WANTED to, but because of my own health issues. Once you understand the role of insulin and starches and sugars and how they effect health, not just for humans, but for dogs, cats, apes, and waterfowl, the whole angel wing being blamed on protein argument totally falls apart.